Matlab Ising model: Anti-ferromagnet

I'm working on a matlab simulation of the 2D Ising model, and would like to verify my code and its results. One thing I'd like to try and observe is the transition from anti-ferromagnet to ferromagnet, but I'm not sure how to create the initial lattice in Matlab. I've already made a (pseudo)random lattice of spins and one that starts as a ferromagnet.

In other words, how can I create a lattice with alternating elements (1s and -1s)?

Also, is there a way to plot or graph my matrix as a colour/greyscale grid, so that -1s are black and +1s are black say? Currently I've used a surface plot but have to rotate the 3D image to a plan view.

As an additional point. I'd also like to calculate the thermal average of magnetisation and Energy [itex]<M>,<E>[/itex] as a function of temperature. I'm not quite sure how to do this with a Monte Carlo algorithm, without a partition function. Is the best way to run the alogrithm for different temperatures then average the results for each temperature?

Also, is there a way to plot or graph my matrix as a colour/greyscale grid, so that -1s are black and +1s are black say? Currently I've used a surface plot but have to rotate the 3D image to a plan view.

try "doc imagesc"
you can call options to customize the colors, read up on it.